Add error about fill_missing/2 with decimals

lib/explorer/backend/series.ex

@@ -18,6 +18,7 @@ defmodule Explorer.Backend.Series do
           | Time.t()
           | NaiveDateTime.t()
           | Explorer.Duration.t()
+          | Decimal.t()
 
   @type non_finite :: Explorer.Series.non_finite()
   @type option(type) :: type | nil

lib/explorer/polars_backend/native.ex

@@ -319,6 +319,7 @@ defmodule Explorer.PolarsBackend.Native do
   def s_fill_missing_with_atom(_s, _value), do: err()
   def s_fill_missing_with_date(_s, _value), do: err()
   def s_fill_missing_with_datetime(_s, _value), do: err()
+  def s_fill_missing_with_decimal(_s, _value), do: err()
   def s_greater(_s, _rhs), do: err()
   def s_greater_equal(_s, _rhs), do: err()
   def s_head(_s, _length), do: err()

lib/explorer/polars_backend/series.ex

@@ -657,6 +657,8 @@ defmodule Explorer.PolarsBackend.Series do
         is_boolean(value) -> :s_fill_missing_with_boolean
         is_struct(value, Date) -> :s_fill_missing_with_date
         is_struct(value, NaiveDateTime) -> :s_fill_missing_with_datetime
+        is_struct(value, Decimal) -> :s_fill_missing_with_decimal
+        true -> raise "cannot fill missing with value: #{inspect(value)}"
       end
 
     Shared.apply_series(series, operation, [value])

lib/explorer/series.ex

@@ -4506,6 +4506,8 @@ defmodule Explorer.Series do
   defp cast_to_ordered_series({:duration, _}, %Explorer.Duration{}),
     do: :duration
 
+  defp cast_to_ordered_series({:decimal, _precision, _scale} = decimal, %Decimal{}), do: decimal
+
   defp cast_to_ordered_series(_dtype, _value),
     do: nil
 

native/explorer/src/series.rs

@@ -1,7 +1,7 @@
 use crate::{
     datatypes::{
-        ExCorrelationMethod, ExDate, ExNaiveDateTime, ExRankMethod, ExSeriesDtype, ExTime,
-        ExTimeUnit, ExValidValue,
+        ExCorrelationMethod, ExDate, ExDecimal, ExNaiveDateTime, ExRankMethod, ExSeriesDtype,
+        ExTime, ExTimeUnit, ExValidValue,
     },
     encoding, ExDataFrame, ExSeries, ExplorerError,
 };
@@ -559,6 +559,22 @@ pub fn s_fill_missing_with_boolean(
     Ok(ExSeries::new(s))
 }
 
+#[rustler::nif(schedule = "DirtyCpu")]
+pub fn s_fill_missing_with_decimal(
+    _series: ExSeries,
+    _decimal: ExDecimal,
+) -> Result<ExSeries, ExplorerError> {
+    // We need to make sure that the series dtype is aligned with the decimal's scale.
+    // let s = series
+    //     .decimal()?
+    //     .fill_null_with_values(decimal.signed_coef())?
+    //     .into_series();
+    // Ok(ExSeries::new(s))
+    Err(ExplorerError::Other(
+        "fill_missing/2 with decimals is not supported yet by Polars".to_string(),
+    ))
+}
+
 #[rustler::nif(schedule = "DirtyCpu")]
 pub fn s_window_sum(
     series: ExSeries,